what makes a good bonsai?
1.) most important, a good, interesting trunk. You don't have that yet. To thicken a trunk you need to let it grow. You also just dug it up. You need to grow roots, to grow the trunk, and for that you need foliage.
If it were mine, I'd let it grow undisturbed, no pruning for at least this year. Then next year move it to a 3 gallon nursery can in 2017. Still no pruning. Let it get tall and bushy, 6 feet tall is not unreasonable. You need height to thicken the trunk. After the trunk is over 2 inches in diameter, chop it down to 4 to 6 inches. Then let it grow out again. when the second segment of trunk is over 1.5 inches, chop it down within 2/3rds the length of the first segment, and then grow your 3rd segment of trunk. It is a slow process to build a tree from scratch, but it can be done. Most people forget that most display ready bonsai spent most of their bonsai training with trunks and branches many feet taller than the final tree.
Once you put a tree in a small bonsai pot, the trunk pretty much stops growing in diameter. So let it develop a nice big mass of roots, to support rapid growth. Let it grow out to develop diameter of trunk. That way when you chop back it will back bud vigorously and give you lots of choices for branches.
It looks like a mountain ash, genus Sorbus. They make nice flowers anf fruit, are in the rose family. Good choice for bonsai. Though just from your pictures my guess could be wrong. But if it is Sorbus, it should be winter hardy for you.